1. The Field of the Invention
The present invention relates to airbag inflation systems in motor vehicles. More specifically, the invention relates to an airbag diffusion system for diffusing inflation gases exiting a curtain airbag inflator.
2. Technical Background
Inflatable airbags are well accepted for use in motor vehicles and have been credited with preventing numerous deaths and injuries. Some statistics estimate that frontal airbags reduce the fatalities in head-on collisions by 25% among drivers using seat belts and by more than 30% among unbelted drivers. Statistics further suggest that with a combination of seat belt and airbag, serious chest injuries in frontal collisions can be reduced by 65% and serious head injuries by up to 75%. Airbag use presents clear benefits and vehicle owners are frequently willing to pay the added expense for airbags.
A modern airbag apparatus may include an electronic control unit (ECU) and one or more airbag modules. The ECU is usually installed in the middle of an automobile, between the passenger and engine compartments. If the vehicle has a driver airbag only, the ECU may be mounted in the steering wheel. The ECU includes a sensor which continuously monitors the acceleration and deceleration of the vehicle and sends this information to a processor which processes an algorithm to determine if the vehicle is in an accident situation.
When the processor determines that there is an accident situation, the ECU transmits an electrical current to an initiator in the airbag module. The initiator triggers operation of the inflator or gas generator which, in some embodiments, uses a combination of compressed gas and solid fuel. The inflator inflates a textile airbag that cushions a passenger during impacts to prevent injury to the passenger. In some airbag apparatuses, the airbag may be fully inflated within 50 thousandths of a second and deflated within two tenths of a second.
An airbag cover, also called a trim cover panel, covers a compartment containing the airbag module and may reside on a steering wheel, dashboard, vehicle door, along a vehicle roof rail, vehicle wall, or beneath the dash board. The airbag cover is typically made of a rigid plastic and may be forced open by the pressure from the deploying airbag. In deploying the airbag, it is preferable to retain the airbag cover to prevent the airbag cover from flying loose in the passenger compartment. If the airbag cover freely moves into the passenger compartment, it may injure a passenger.
Airbag apparatuses have been primarily designed for deployment in front of an occupant between the upper torso and head of an occupant and the windshield or instrument panel. Conventional airbags, such as driver's or passenger airbags (hereinafter referenced as the “primary airbag”), protect the occupant's upper torso and head from colliding with a windshield or instrument panel.
Airbag technology has advanced to include airbag apparatuses which protect occupants during a side impact, or roll-over accident. In these accidents, the occupant may be thrown against the windows, doors and side-walls of the vehicle. These airbag apparatuses are known as curtain airbags. Generally, the curtain airbag is attached to a thin long frame member which runs along a side of the roof of the vehicle. Often due to window size and visibility requirements, the curtain airbag apparatus has a long thin shape.
Generally, the airbag of a curtain airbag apparatus inflates and descends from the frame member to cover a majority of the area between the occupant and the side of the vehicle interior. The inflated airbag appears much like a curtain covering the vehicle window. The curtain airbag may protect the occupant from impact with a side window, flying shards of glass, and other projectiles. The curtain airbag may also help to keep the occupant inside the vehicle during a roll-over accident.
Generally, the un-inflated curtain airbag is installed in a very limited thin space defined by the roof frame member. Accordingly, the inflator may be a thin, cylindrical member which extends a portion of the length of the curtain airbag. In this manner, the curtain airbag inflator is capable of providing sufficient inflation gas to properly inflate the curtain airbag.
Generally, the inflator is installed within the textile bag of the curtain airbag apparatus. However, doing so generally requires the inflator to include a diffuser. Gas which fills the curtain airbag is generated by the ignition of gas generant within the inflator. Generally, the gas is created from the rapid burning of pyrotechnic materials.
The gas (also referred to herein as exhaust gas) escapes exit ports in the inflator at a high velocity and temperature. Due to the limited space, the textile bag is generally stored by folding it up against the inflator. Without a diffuser, the hot gas is concentrated on the textile bag. The concentrated hot gas and the confined space may combine to cause the gas to burn one or more holes in the airbag material, which is generally a nylon or polyester weave. The holes may cause the curtain airbag to inflate improperly.
A diffuser disperses the exhaust gas. Dispersing the gas allows the gas to expand and cool. A diffuser may also include a surface which further allows the gas to transfer some of its heat. A diffuser may be used to direct the gas leaving the exit ports. Gas may be directed to cause the textile airbag to inflate in a particular manner. Once the gas passes through a diffuser, the gas is sufficiently cooled and/or not concentrated to prevent burning holes in the textile airbag.
Additionally, the gas may be directed through an exhaust passage to allow the gas to further cool before entering the airbag. Conventionally, exhaust passages are structures formed between the inflator and the diffuser. These exhaust passages occupy valuable space when the diffuser and inflator are installed and not in use. Space occupied by exhaust passages may be used to provide a more safe and/or aesthetically pleasing installation area for the airbag apparatus.
A diffuser may be built as part of the body of the inflator. Generally, doing so adds to the production and design costs of the inflator. Alternatively, separate parts may be secured to the inflator at appropriate points to function as diffusers and to direct the exhaust gas. Alternatively, one or more parts may be secured to each other to form the diffuser. Securement may be accomplished using a weld or other conventional technique. Such securement techniques generally increase production time and assembly costs.
When a diffuser is incorporated into the body of the inflator, this may require custom fabrication of inflator bodies including diffuser features for different vehicles. Additionally, non-standard inflator/diffuser combinations may increase training time required for workers assembling the airbag apparatus. Custom fabrication is also expensive.
Additionally, conventional diffusers may include parts or sections that must be positioned to properly obstruct gas exit ports of an inflator. For example, the diffuser and inflator may need to be radially oriented with respect to each other to ensure proper operation of the diffuser. This adjustment adds delay and a skill requirement in the assembly process of the completed airbag apparatus.
Accordingly, it would be an advancement in the art to provide an airbag diffusion system which is simple to fabricate. It would be a further advancement to provide an airbag diffusion system which directs the gas using a standardized inflator. Additionally, it would be an advancement in the art to provide an airbag diffusion system which prevents concentrated gas jets and cools the gas exiting the inflator to prevent holes in the airbag material. A further advancement in the art would be to provide a diffusion system and method of fabrication having minimal expense. Additionally, it would be an advancement in the art to provide an airbag diffusion system which is compact to allow the system to be installed in areas of small dimensions relative to conventional diffusion systems. It would be a further advancement in the art to provide a diffusion system that does not require rotational alignment of diffuser members and gas exit ports. The present invention provides these advancements in a novel and useful way.